Lag after visiting certain lot?

I'm glad that worked for you. :) I don't usually have lag either, and on the odd occasion I do experience something like you just did, Error Trap usually resets someone (a stuck someone) a short while later, and it goes away. Anytime anything gets a little off that Error Trap doesn't catch, a town reset like you did usually takes care of it for me. You're right that worlds/saves start to have some issues over time, but the nraas mods really do a good job of keeping a lot of that under control. Sometimes people move their households periodically to another world for a fresh start, too, which can be helpful. I was thinking you recently came back to S3 and this is probably a fairly new save for you, though, so I wouldn't expect you to be at point where you'd need to do that.

Edited to add: I realized later it's probably Overwatch that does the unsticking/resetting :D but anyway, both mods have really helped my games over the years.